1056795 - Optimize ArrayPushDense

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

[Jan de Mooij [:jandem]]

Attachment: Patch

jit::ArrayPushDense is the slow path for inlined Array.push calls. It forwards to js::array_push, but that function is too generic/slow. On Octane-deltablue we spend about 5% under ArrayPushDense.

The attached patch adds a fast path to jit::ArrayPushDense. It improves the micro-benchmark below from 894 to 715 ms and wins at least a few hundred points on deltablue.

Now with GGC we could also add a JitCode stub to handle reallocating/copying the elements without any VM calls, but that's a lot more work and this is a very easy win for now.

function f() {
    var t = new Date;
    for (var i=0; i<1000000; i++) {
	var arr = [];
	for (var j=0; j<130; j++)
	    arr.push(j);
    }
    print(new Date - t);
}
f();

Comment 1

[Jan de Mooij [:jandem]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/a4877238de09

Comment 2

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/a4877238de09